This application claims the priority of German Application Number 199 56 264.4, filed in Germany, Nov. 23, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a process for cleaning an open-end spinning rotor, comprising a rotor cup having a fiber collecting groove and being arranged in a vacuum chamber, which, while leaving an air current transfer gap between the inside of the rotor cup and the vacuum chamber, can be closed over by a movable cover, which comprises an extension projecting into the inside of the rotor cup, which extension comprises a mouth of a fiber feed channel as well as a first part of a yarn withdrawal channel, and which extension can be removed from the inside of the rotor cup when the cover is moved away, said process comprising:
interruption of the fiber feed in the event of an end-break slowing down the open-end spinning rotor PA1 moving away of the cover from the vacuum chamber to insert cleaning elements into the rotor cup, and PA1 closing of the vacuum chamber after cleaning. PA1 a momentary moving away of the cover from the vacuum chamber for the purpose of temporarily removing the extension from the inside of the rotor cup, before the open-end spinning rotor is so slowed down that the fibers present in the rotor cup are no longer held in the fiber collecting groove by the centrifugal forces, and PA1 a closing of the vacuum chamber after the fibers present in the rotor cup cannot be held any longer in the fiber collecting groove by centrifugal forces due to the further slowing down of the open-end spinning rotor.
The present invention relates further to an apparatus for carrying out the process.
A process of this type is prior art in U.S. Pat. No. 4,825,631. In this process, the cleaning of the open-end spinning rotor is carried out in connection with an end break and a subsequent piecing process. After the fiber feed is interrupted, the open-end spinning rotor is slowed down by a traveling maintenance device, the rotor cup is uncovered by swivelling away a cover from the vacuum chamber for the purpose of inserting cleaning elements and after the completed cleaning, the vacuum chamber is closed.
The known process has in the past proved satisfactory in the case of rotors having standard dimensions, and made use of the fact that after the open-end spinning rotor was slowed down and before the cover was removed from the vacuum chamber, a fiber ring still located in the inside of the rotor cup was suctioned off by the air current transfer gap. It has been known for a long time from U.S. Pat. No. 3,481,129 that fibers, which, in the case of an end break, reach the inside of the rotor cup after fiber feed has been stopped, find--at reduced rotor speeds--their way to the operational suctioning as long as the vacuum chamber is still closed. The air current transfer gap must, however, have accordingly large dimensions, which is why it is suggested in the above mentioned patent that the extension of the cover which projects into the rotor cup is provided with a corresponding recess.
It has been shown in practice that, especially in the case of small rotor cups, whose fiber collecting grooves have a diameter of less than 30 mm, the fibers do not always find their way into the operational suctioning. An explanation for this is supplied in the non-generic German published patent application 41 31 684, whereby a fiber ring which is to be removed from the rotor cup can cling on to the extension of the cover which projects into the rotor cup. This publication deals, however, in contrast to the above mentioned prior art, with the cleaning of the open-end spinning rotor by means of air pressure and with a closed spinning aggregate.
The statement that fibers to be suctioned off can remain on the extension of the cover when the spinning aggregate is closed has been confirmed in practice. In particular in the case of synthetic fibers, the fiber ring located in the fiber collecting groove contracts somewhat due to its elasticity after the open-end spinning rotor has been slowed down, so that its diameter is reduced. The fiber ring thus reaches the extension of the cover and, after a time, can block the mouth of the fiber feed channel, so that a subsequent piecing process becomes impossible. A fiber ring located on the extension of the cover cannot be removed by normal cleaning elements after the cover has been moved aside, as the cleaning elements penetrate primarily into the inside of the rotor cup and are not arranged at the extension of the cover.
It is an object of the present invention to take measures to effectively prevent the fiber ring from remaining on the extension of the cover before the cover is actually moved aside for the purpose of inserting cleaning elements into the rotor cup.
This object has been achieved in accordance with the present invention in that before the actual moving aside of the cover for the purpose of inserting cleaning elements into the rotor cup, the following procedural steps are additionally carried out:
According to the present invention, the extension, at a certain time at which the fiber ring is still held fast in the fiber collecting groove, is removed so far out of the rotor cup so that the fiber ring cannot cling on to the extension when it contracts in diameter as the centrifugal forces become weaker.
During the subsequent momentary re-closing of the vacuum chamber, the fiber ring thus reaches the operational suctioning device without any difficulties. The cover can then be moved aside in the usual way for the actual cleaning of the open-end spinning rotor.
The temporary re-closing of the vacuum chamber does not, of course, need to be carried out fully, and the cover does not need to be locked into its operational position again. It is sufficient to execute the closing movement only to such a degree that the suction effect of the vacuum chamber is again effective in the inside of the rotor cup. In practice, a ring seal applied to the cover can be disposed only lightly on the vacuum chamber.
The process can be carried out in principle in a number of different ways. For example, it is sufficient when the slowing down of the open-end spinning rotor is begun only during or after the momentary moving away of the cover from the vacuum chamber. This ensures in any case that the extension is removed from the rotor inside before the fiber ring collapses. Alternatively, it is, of course, possible to start the slowing down of the open-end spinning rotor before the temporary moving away of the cover from the vacuum chamber. In the latter case, the time lapse must be ensured so that the fiber ring is held completely in the fiber collecting groove until the extension has been moved out of the rotor cup. This is usually the case when the slowing down is started approximately 1.5 to 2 seconds before the cover is moved aside.
In order to ensure that the extension does not reach the rotor inside too early when the vacuum chamber is being closed, the temporary moving away of the cover from the vacuum chamber can be delayed until the open-end spinning rotor comes to a complete standstill.
In the case of an apparatus for carrying out the process, a maintenance device is advantageously arranged at the spinning aggregate, which maintenance device is provided with apparatus for activating a braking device, apparatus for opening and closing the vacuum chamber as well as apparatus for inserting cleaning elements in the rotor cup. The apparatus for opening and closing the vacuum chamber are coordinated, according to the present invention, with the apparatus for activating the braking device in such a way that (a) in the case of a partly slowed down open-end spinning rotor, the cover is moved far enough away from the vacuum chamber so that the extension is removed from inside of the rotor cup and that (b) after the open-end spinning rotor has come to a complete standstill, the vacuum chamber is again closed before (c) the cover is moved away from the vacuum chamber for the purpose of inserting the cleaning elements in the rotor cup.
Advantageously, the apparatus for activating the braking device comprises a brake lever and the apparatus for opening and closing the vacuum chamber comprises an opening lever. The brake lever and the opening lever are each connected to a cam disk drive. This results in a set arrangement of the individual timed sequences.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.